Thermal constraints are a typical limitation on the power that may be generated by air breathing gas turbine engines. Components such as the turbine nozzle and the vanes thereof as well as the turbine wheel and blades thereon cannot be subjected to gases of combustion at temperatures in excess of some predetermined temperature without either shortening the life of the engine or requiring resort to expensive, exotic materials which make the cost of manufacture of the engine uneconomical. Thus, for a gas turbine engine having a combustor of given size, the ultimate power output is not always so much limited by gas generating volume associated with combustion as by the ability of the design to allow operation without exceeding temperature limits at the turbine nozzle and at the turbine wheel.
Recognition of this factor suggests that a given turbine engine could be uprated by increasing the combustor volume power density which can be obtained by maximizing the combustion flame zone within a given combustor volume.
One limitation on the combustion flame zone size resides in the physical location of the combustor walls with respect to each other and the combustor volume they define. Conventionally, an increased flame zone is attained by spreading the walls to increase the volume of the combustor. This, however, increases the size of the engine and in essence, is a re-design of a whole new engine as opposed to an uprating of an existing one. The other constraint on flame zone size is limitations on the amount of the combustor volume that is available for combustion. Conventionally, the total interior volume of the combustor is not available for combustion for the reason that various devices are employed on the interior walls to generate film air cooling of such walls to prevent the combustor itself from overheating or for otherwise introducing dilution air. Clearly, combustion cannot occur in those areas where film air cooling or the like is intended to occur without damaging the combustor and so the potential combustion flame zone for such a combustor is reduced by the volume devoted to the provision of means for providing film air cooling or the like.
The present invention is directed to recovering that part of the volume of a combustor heretofore used for film air cooling and utilizing it to increase the combustion flame zone for that combustor. That in turn will increase the power density of the combustor which in turn will allow the gas turbine to be run with a greater output, that is, to be uprated.